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Natural Bridges named the world's first international dark-sky park

Nearly 100,000 people stop at Natural Bridges National Monument in southeast Utah each year but only a fraction of those visitors see its most spectacular vistas, the Night Sky.

Granted, the daytime landscapes at the national monument are particularly fetching, but the night sky? “Amazing,” Grand Junction, Colo., geologist and astrophotographer Terry Acomb says. “There is a tremendous contrast between the bright night sky of stars and the dark canyon walls…it’s just beautiful out there.”

The beauty of the night sky, the lack of light pollution, and the National Park Service commitment to night skies as a natural resource, led the International Dark-Sky Association this spring to designate Natural Bridges National Monument as the world’s first International Dark Sky Park.

Natural Bridges is one of the darkest national parks in the country according to a comprehensive study of night sky quality conducted by the National Park Service.

Just how dark is it? “It’s the only Bortle class 2 sky they’ve documented,” said Chris Luginbuhl of the U.S. Naval Observatory in Flagstaff, Arizona., and a board member of the International Dark-Sky Association. “In plain English that means it’s the darkest or starriest sky they’ve seen while doing these reviews. The Bortle system is a 10-level scale with one and two being the darkest skies and 10 having the most light pollution.”

The International Dark-Sky Association’s Dark-Sky Park Program challenged Natural Bridges to minimize its own nocturnal impact and share the magnificent starry sky with park visitors.

Responding to the challenge meant changing a lot of light bulbs. More than 80% of the light fixtures have been modified, making them dark-sky-friendly by shielding them so all the light points downward.

Most of these outdoor fixtures utilize 13-watt compact fluorescent light bulbs that provide ample light but prevent stray light from the visitor center and park ranger residences from interfering with campgrounds and the backcountry.

On a clear night - and there are many each year in this dry, rugged land - the park’s dreamy night sky reveals the Milky Way galaxy and a jillion or so stars and planets. Acomb, and other night sky photographers, have been to the park for years, capturing visits from interstellar celebrities like Comet Hale-Bopp.

During the summer, the park provides astronomy ranger programs under spectacular starry skies.

Starry skies are recognized by the National Park Service as part of the scenery of the park, and management guidelines encourage parks to minimize light pollution whenever possible.

The benefits go beyond stargazing. “Natural Bridges has reduced its operational costs and energy use by upgrading its outdoor lighting, creating a better habitat for nocturnal wildlife, and improving visibility and safety at night,” says park Superintendent Corky Hays. “I hope our national parks can continue to provide a clear view of the heavens that so many of us have lost from our backyards.”